Natural clays have been used for treatment of gastrointestinal disorders since at least before 300 B.C. The following is an excerpt from the Hoover translation of Re De Metallica, Dover Publications, New York, N.Y., Book II, p. 31 (1950).
" . . . a hill in the island of Lemnos . . . in the northern Aegean Sea has produced this `earth` . . . reddish-yellow clay . . . from before Theophrastus' time (372-287 B.C.) down to the present day. According to Dana (System of Mineralogy 689), it is cimolite, a hydrous silicate of aluminum. The Ancients distinguished two kinds--one sort used as a pigment, and the other for medicinal purposes. This latter was dug with great ceremony at a certain time of the year, molded into cubes, and stamped with a goat--the symbol of Diana. It thus became known as terra sigillata, and was an article of apothecary commerce down to the last century. It is described by Galen (xii., 12), Dioscorides (v., 63), and Pliny (xxxv., 14), as a remedy for ulcers and snake bites."
The time-honored history of the medicinal use of natural clays continues today. Kaolin, for example, is described in the Merck Index, Tenth Edition, (Monograph 5119, p. 759) as a "white or yellowish-white earthy mass or white powder"; and that it is "prepared for pharmaceutical or medicinal purposes by levigating with water to remove sand, etc". Its Therapeutic Category is given as "Adsorbent", and its Veterinary Therapeutic Category as "Topical and G.I. (gastrointestinal) adsorbent. Poultice". Also, remedies for diarrhea that use clay may be purchased over the counter in most pharmacies. In a local pharmacy in N.J., for example, one of us found three different brands of tablets under the names of Kaopectate (Upjohn), Rheaban (Leeming Div., Pfizer), and Diar-Aid (Thompson Medical Co.). The labels on all of these showed the active ingredient to be Attapulgite, each tablet containing 600 (or 750 mg) of this component along with inert materials or adjuvants such as zinc or magnesium stearate, colloidal SiO.sub.2, TiO.sub.2, starch, etc.
The zeolite minerals, another type of hydrous aluminosilicates which like clays have been known since ancient times, received little attention from mineralogists and others until about 30 years ago, most probably due to the relative scarcity of these minerals. This neglect changed radically with the first successful commercialization by Union Carbide Corporation of a synthetic crystalline zeolite known as "Linde-5A". Since that time a number of synthetic zeolites, some having no known mineral counterparts, have been prepared and successfully exploited as industrial adsorbents and catalysts. This in turn led to awakened interest in natural deposits of mordenite and erionite, for example, which are now known to be extensive. For a description of the structure, chemistry and use of natural and synthetic crystalline zeolites, see "Zeolite Molecular Sieves", Donald W. Breck, published by John Wiley and Sons, New York, N.Y. (1974), incorporated herein by reference for background.
Attention was first brought to adding zeolites to animal feed in the 1960's by the Japanese who used it on chickens and pigs to alleviate fecal odor. It was found that such practice also showed benefits in weight gain and general health (i.e. in improved performance) of the animals. A growing amount of research on zeolites as dietary supplements for animals has since taken place, as indicated, for example, by the twenty-nine papers presented at the 1982 meeting in Pottsdam, N.Y. by researchers from the USA, Japan, China, Chechoslovakia, Bulgaria, USSR, and Italy. See "Zeo-agriculture, Use of Natural Zeolites in Agriculture and Aquaculture", edited by W. G. Pond and F. A. Mumpton, Westview Press, Boulder, Colo., 1984, incorporated herein by reference for background purposes. Studies were reported on pigs, chickens, cattle, and fish. Although the editors comment that many of the results lack agreement, the following noteworthy points are made in the foregoing publication: evidence is available and generally agreed upon for improved performance of swine, ruminants, and poultry fed zeolite-supplemented rations; a possible physiological explanation for the improved performance is the known binding action for NH.sub.4 + of zeolites and reduction of portal blood ammonia from the gastrointestinal tract; if dietary antibiotics promote growth by suppressing ammonia formation in the gastrointestinal tract, this could at least in part explain the similar growth response induced by dietary zeolites.